Manufacture of abrasive articles



April 23, 1935.

A. L, BALL ET AL 3,998,919

MANUFACTURE OF ABRASIVE ARTICLES Filed NOV. 12, 193]. I

KSheets-Sheet 1 a NTORS RT 1.. mu, BY RAYMDND C. BENNER ATTORNEY Aprii3, 19350 A. L. BALL ET AL MANUFACTURE OF ABRASIVE ARTICLES 5Sheets-Sheet 2 Filed Nov. 12, 1951 fzy 8.

. INVENTORS .,AL 5RT 1.. BALL VBY RAYMDND C. BENNER flmw/ ATTORNEY A ril23, 1935. A. 1., BALL El AL MANUFACTU RE OF ABRASIVE ARTICLES 3Sheets-Sheet 3 Filed Nov. 12, 1931 INVENTORS ALBERT 1,. BALL EAYMOND c.BENNER.

ATTORNEY Patented Apr. 23, 1935 UNITED STATES insane PATENT oFFicE.

Niagara Falls, N. Y.,

assignors to The Carborundum Company, Niagara Falls, N. Y., acorporation of Pennsylvania Application November 12, 1931, Serial No.574,532

12 Claims.

\ This invention relates to improvements in the manufacture of abrasivearticles and is applicable to abrasive wheels intended for peripheralgrinding although not limitedto this method of grinding.

A typical operation .in which abrasive wheels are subjected totemperature changes is that of grinding wood to produce paper pulp.Wheels intended for this type of service must resist changes at leastfrom minus 40 degrees centigrade to plus 100 degrees centigrade. Theyfurthermore must be made very rugged mechanically, in order to performunder loads as high as 2000 horsepower. They are made in sizes as heavyas eight tons, requiring a sixteen inch diameter steel spindle, and aremounted between right and left-hand threaded flanges to guarantee theirproper mechanical functioning and safety.

The serious trouble encountered in the operation of an artificialabrasive wheel for suchpurposes is the building up of excessive flangepressure which may lead to the destruction of the wheel. I I

- The more important causes of flange pressure are due (1) to the largedriving torque, and (2) to differential expansion between steel spindleand abrasive body caused by temperature changes. The pressure due to thefirst'cause may amount to from 500 to 900 pounds per square inch underthe flange and is not serious; in fact, it isessential in order that thewheel may perform its work. The increase in pressure due to temperaturechange, such as cooling the wheel from 100 degrees centigrade to degreescentigrade, however, may amount to three or four thousand pounds persquare inch, and it is the magnitude of these secondary pressures actingupon the abrasive that, to a large degree, causes cracking of suchwheels.

A large abrasive wheel, such as is used for pulp grinding, is madealmost invariably of material that has a lower coefficient of thermalexpansion r than the steel shaft'upon which it is mounted.

The flanges that grip the sides. of the wheel are Q threaded in left andright-hand directions re- 3 J both expand, the shaft lengthens more thanthe abrasive body. During this change, however, the power continues totake up this increase in shaft length and preserves the. tight flangegrip upon the wheel. When the assembly cools, there is 55 absolutely norelief from theforces' generated by the steel shaft while trying tocontract to its normal length when cool. The abrasive cannot contractsufficiently to afford the necessary relief; consequently, high,pressures upon the abrasive result. If an abrasive wheel is capable ofresisting the first few cycles of heating and cooling (possibly as aresult of a slight disintegration of the cement grouting material orinadequately resilient gasket materials such as are commonly used underthe driving flanges) the repeated cycles of operation'cause the sameextra tightening of the flanges, and cooling reapplies the same heavyflange pressure with its attendant threat upon the physical integrity ofthe wheel.

There are two broad classifications into which assembly methods forthese large Wheels fall; viz, (1) those which provide a ribbed metallichub or drum structure wherein the rotating forces are applied to theabrasive entirely by means of large ribs which are inserted into theabrasive and which ribs are parallel to the driving shaft and contactwith the abrasive essentially throughout the length of the arbor hole,and (2) those which provide no hub in the arbor hole, but which drivethe wheel entirely by pressure directed upon the wheel by the flangesOur invention has principally to do with the second type of mounting andwith providing means for eliminating the excess flange pressureordinarily caused by an abrasive assembly being subjected to temperaturechange.

In our invention, we provide combinations of thermal and elastic meansfor neutralizing 'the differential expansion between the abrasive andthe steel shaft by 'placingunder the flanges one of the followinga 1.Springs ofhighly elastic properties which permit the proper amount ofshaft contraction with no substantial increase in flange pressure;

2. The proper thickness of a material, such as sulfur, having a veryhigh coeflicient of .thermal expansion to make the net coefficient ofabrasive annulus the same as that of the shaft; or

3. A combination of the two classes of materials described under 1 and 2above, which may be accomplished by materials such as synthetic resinswith a relatively small percentage of inert filler. Such compoundspossess a high coefficient of thermal expansion and are also veryelastic in behavior. I 50 Changes in the dimensions of a solid may takeJ place because of heating, because of the application of force orbecause of the combination of both heat and force. In the first of theseeffects, the important factor is the coeflicient of thermal expension,while in the effect of force the important factors are compressibilityand elasticity. We make use of both of these effects for the substancesused in carrying out temperature com pensa'tion in our invention inconjunction with 7' wheel and its driving flanges;

til

Figure 2 is an end view of the wheel shown between the flange and wheelin Figure 1;

Figure 3 shows axial'sections. of a composite bushing shown in Figure 1,the component parts being separated for clearness;

Figure 4 is a perspective view of a corrugated spring shown in Figure 3Figure 5 is an end view of part of the come posite bushing shown inFigure 3;

Figures 6 and 7 are views similar to Figures 1 and 2respectively'showing a modifled form of mounting;

Figures 8 and 9 are longitudinal (partly sectional) and half sectionalend views, respectively, of another modified form of mounting;

Figures 10 and 11 are longitudinal (partly sectional) and end views,respectively, of a modi fled embodiment of our invention; and

Figures 12 and 13 are side and end views, respectively, of a mountedabrasive wheel in which the abrasive wheel is of segmental structure.

Figures 1 andji are views showing a method for carrying out ourinvention by interposing the permanently elastic mechanical system at M,

if and I3 between abrasive annulus I and flange 3 which provides thenecessary degree of freedom to permit relative movement between theabrasive and shaft when the assembly is subjected to temperature changesand at the same ime provide for the necessary flange pressure to drivethe wheel.

Figures. 6 and 7 illustrate another method of carrying out ourinvention. The highly expansive and elastic material l6, when interposedin suitable thickness between flanges 3'and abrasive annulus l, servesto compensate for the dif-- ference in expansion between the abrasive iand steel shaft 2. This compensation, it will be seen, is the fullequivalent of the compensation obtained by making the thermal expansionsof abrasive and shaft equal.

Figures 8 and 9 are drawings of still another modification for carryingout our invention. ;A brief study of these illustrations will show thathub is is. essentially an enlargement of shaft 2 and that the highlyexpansive substance itbetween thehub flanges 2t and abrasive lcompensates for or prevents the accumulation of stresses due to thermalchange in a manner similar to that described in the immediatelypreceding para Figures is and 11 illustrate a method of using ourinvention in combination with a different type of mounting than thosementioned above. The use of iron tie rods ii, which connect the flangess and which function expressly as bolts to produce the necessary flangepressure against the abrasive wheel perrnit the shaft, flanges and boltsto be considered as a mechanical unit composed of p'artswhosecoefficients of thermal expansion are the same. The highly expansivematerial it, placed under flanges 3, is essential to compensate for thedifferences in coeiilcient of expansion between the mechanical unit andthe abrasive annulus in the manner mentioned in the preceding paragraph.

Referring to Figures 1, 2, 3, 4 and 5 of the drawings, we will disclosein full detail our first method for carrying out our invention. InFigure 1, the abrasive annulus l is held in its axial positionrelatively to the shaft 2 by means of clamping members or opposeddrivingflanges 3. These flanges are threaded on the driving shaft bymeans of right-hand and left-hand engagement, respectively, as indicatedat 8 in Figure l. The direction of rotation of the wheel is such thatincrease of load increases the axial pressure on the abrasive. A'mechanical system 55, embodying permanently elastic structural features,is placed between at least one of the driving flanges and the.

abrasive annulus I. The members included in the structural combinationI5 include a back plate H, a frontplate l2, and a series of corrugatedsprings disposed between the front and; back plates and having theirgreatest dimensionsextending radially with respect to the axis ofrotation. The combination is shown in detail in Figures 3, 4 and 5.These springs are corrugated so as to resist close approach of the backplate H toward the front plate 12. Interlocking lugs B are shown on thefront plate and also on the back plate. Each of these lugs fits intoa'corresponding recess in the opposing member. This eliminates anytendency for the wheel to sag in its mounting. The lugs also serve toretain the corrugated springs ill in their radial position between thefront and back plates. When'the front and back plates and theintermediate spring members are assembled, bolts which passthrough theholes it are tensioned (by means of'nuts) sufliciently to enable theannular combination to be assembled in place'between a driving flangeand the wheel without causing, however, any appreciable compression ofthe corrugated springs.

In this method of carrying out our invention it is plied to the designof the abrasive wheel assembly it will be found,.'when the wheel iscooled from the highest temperature of operation, that the 1longitudinal (axial direction) contraction of the shaft 2, relatively tothe abrasive annulus i, will take place without causing undue stress inthe abrasive wheel.

A second method in which our invention may be carried out is shown inFigures 6 and '7. in

the modification'illustrated by these figures, the

driving flanges it are mounted on the driving shaft in the same manneras described in connection with Figures 1 and 2'2. As the abrasive wheelis rotated, the effect of increasing load is to make the flangescontinually press the wheel more tightly until the maximum; loadingconditions are met. To take care of the differential thermal expansionbetween the shaft 2 and the abrasive annulus 9, rings it are inserted asshown inFig. 6 between the driving flanges and the abrasive. Preferablythe material of which it is composed should have a relatively highcoefficient of thermal expansion (to to toxinper centigrade degree orhigher). We have found that by' the use of such highly expansiblematerial for the annulus l6 (and giving it an appropriate axialdimension) a thermally compensated assembly may be constructed asindicated in Fig. 6. By way of example, we may take the length of theabrasive between the flanges as 54 inches.- The material l6 may becomposed of 90 per cent of sulphur and 10 per cent of finely pulverizedcoke and should be 2 inches to 2% inches thick under each flange tocompensate for the difierence in expansion coefiicients of the abrasiveand the shaft. This material is placed in position (between the drivingflanges and the abrasive) by pouring. Since the melting point of sulphuris approximately 114 degrees centigrade, and since the material is veryfluid at 130 degrees centigrade to 150 degrees centigrade, such apouring process is easily carried out by those skilled in the art. Afterhaving been poured into place, the mixture hardens 'as soon as it coolsto 114 degrees centigrade and remains solid attemperatures below thispoint. The hardening temperature is sufliciently above the maximumoperating a temperature of a pulp wheel (100 degrees centigrade) toserve its purpose.

As a further illustration of the second method of carrying out ourinvention, we may mention that the annulus l6 may be made from varioussynthetic resins suitably compounded with a small proportion of flnelygranulated inert filler. The resinous mixture is heat hardened inposition between the driving flanges and the abrasive so that the axialthickness of the insertion is from 1 to 3 inches. The large choice ofmaterials of high coefficients of expansion and controllable elasticmodulus which are thus obtainable permit's compensation for thedifferential expansion of shaft and abrasive wheel.

Referring particularly to the first twocited methods 'of temperaturecompensation, it is un-- derstood that the coefiicient of expansion ofthe mechanical'system composed of members [0, H and I2 shown in Figureslto 5 inclusive may be varied by the selection of the materials of whichthese members are composed so that the net coeiflcient of expansion ofthegsystem is equal to or greater than that of'the shaft (which is,usually about to 11.5 10 per degree centigrade for a steelshaft). Inthis way both the resilience of the spring member ID and the highercoefficient of expansion of the mechanical system (H), H and I!) maycontribute mutually to the compensation for stresses due to thermalchanges:

The first method of carrying out the invention provides-the greater partof the compensation effect from the elastic properties of the'spring andthe remaining smaller effect from the coefllcient of thermal expansionof the mechanical system referred to. In the second method of carryingout the invention, the proportion of these two effects is reversed; thatis, thegreater compensation effect is derived from'the relatively highthermal expansion of the member; I 6 and the lesser effect is derivedfrom the elasticity of the material of which I6 is composed. Therelative degree to which these thermal and elastic properties functionmay be selected by the designer.

A third method of carrying out our invention, as illustrated in Figures8 and 9, may be accomplished thus: 'An abrasive annulus l is providedwith a metallic hub I9 to whichare afilxed hub flanges 20. The highlyexpansive material 16 is The thicknessof the material H5 at locationsmarked M,.i. e., between hub flange 20 and abrasive annulus I, isselected according to the length of the assembly under consideration inorder to counteract thermal change. The thickness of the same materialat location marked Y is quite immaterial (so long as the longitudinalgripping action is not interfered with) and may be selected entirely byconvenience.

It is sometimes desirable in carryingout this method of assembly torelease one of the hub flanges 20 (after having positioned andallowedthe material 16 to harden) and to insert a thin sheet of shim materialsuch'as .002 of an inch to .009 of an inch in thickness of steel betweenthe end of huh I!) and hub flange 29, thereafter solidly tightening thehub flange holding screws 2|. This assists not only in preventingthermal stresses but reduces the cumulative effect of any slightdiscrepancies in design over the range of temperatures to which thewheels are subjected such as minor inaccuracies in determining thermalexpansion coefficients and slight variations in dimensions at M, etc.

The assembly just described is, of course, complete'd for commercialoperating by mounting it in between the driving flanges 3 which aremounted upon shaft 2 in right and left-hand threaded relationshiprespectively, as shown at 8 in Figs. 1, 6, 8 and 10.

Figures 10 and 11 illustrate a method of mounting abrasive wheels whichmay be used in the art. Our invention is adapted to compensate fortemperature changeswhen wheels are mounted in this manner. and 11, itmay be seen that the abrasive annulus I is held in operating positionupon shaft 2 by flanges 3 which are rotatable with'the shaft due to keys9. One, flange is forced firmly against the shoulder I (which is rigidlyassembled upon the shaft by keying, driving, shrinking, or any desiredmethod and the other flange is held securely against'a side of theabrasive wheel. by bolts madefrom-steel or iron of the usualcomposition. Nuts 5 constitute means for producing the amount of flangepressure necessary when using thewheel. The wheel with flanges bolted Byreference to Figures 10 on it is held securely against shoulder 1 by nut6. An assembly as described requires a highly expansive material l6under at least one flange and ential expansion between the abrasive andthe.

steel members If this differential expansion is not corrected, seriousflange pressuresmay result.

Having thus described our invention and included several differentmethods of carryingit out, what we claim as new and desire to secure byLetters Patent is embodied in the following.

claims.

. We claim:

' '1. As an article of manufacture, an artificial abrasive wheel adaptedfor peripheral grinding wherein the power is transmitted from opposeddriving flanges which press axially against the 'wheel, and wherein anannular member is disposed between one of the flanges and the wheel,said annular member having a coefficient of expansion which'compensat'esin an axial. direction for the difference between the respective thermalexpansions of the wheel and of the supporting means. 1

2. As an article of manufacture, an artificial abrasive wheel adaptedfor peripheral grinding, and driving means for said wheel comprising ashaft, a pair of opposed driving flanges mounted to turn on said shaftby right and left-hand threaded engagement respectively to hold thewheel between them, and a permanently elastic member mounted between oneof said flanges and the abrasive wheel, said permanently elastic membercomprising a front plate, a back plate and a plurality of corrugatedsprings interposed between the front plate and the back plate so thatthe springs extend in a general radial direction on application ofincreased pressure from the flanges.

3. As an article of manufacture, an artificial abrasive wheel adaptedfor peripheral grinding and driving means for said wheel comprising ashaft, a pair of opposed driving flanges mounted to turn on said shaftby right and left-hand \threaded engagement respectively to hold thewheel between them, and a compensating annulus interposed between one ofsaid flanges and the abrasive wheel, said annulus having such acoeflicient of expansion and such dimensions that it compensates forrelative changes of length in an axial direction caused by change intemperature in the shaft and abrasive wheel.

4. As an article of manufacture, an artificial to turn on said shaft byright and left-hand threaded engagement respectively to hold the wheelbetween them, and an annular member mounted between said flanges, saidannular memher having aIcoeflicient of expansion at least as high asthat of the driving shaft or abrasive wheel and having also apermanently elastic character whereby stresses arising from temperaturechanges are substantially compensated.

5. An article of manufacture comprising an artificially bonded abrasivewheel, opposed driving flanges adapted to transmit power from thedriving shaft to the wheel, said flanges being mounted on said shaft byrespective right and left-hand threaded engagement therewith toautomatically grip the wheel as the load increases, and a permanentlyelastic member interposed between one of said flanges and the wheel,said member having a coeflicient of expansion and a thickness'whichsubstantially compensate for the differential expansion between thedriving shaft and the wheel while such member is sumciently elastic totake care of residual differences of expansion.

6. A mounting for an abrasive wheel comprising a driving shaft, drivingflanges for said wheel mounted on said shaft by respective right andleft-hand threaded engagement therewith to transmit power to the wheelat opposite side contacts disposed at a substantial distance from saiddriving shaft, and a pressure transmitting mamber between at least oneof said flanges and said wheel, the coefflcient of expansion andthe-thickpower to the wheel with the aid of pressure exerted parallel tothe axis of rotation, and a pressure transmitting member between atleastone of said flanges and the wheel, the coefficient of expansion and thethickness of said member being such as to substantially compensate theaxial differential expansion between the shaft and abrasive wheel. 1

8. A mounting for pulp wheels which are subeflicient to substantiallycompensate for the differential expansion. between the driving shaft andpulp wheel measured in a direction parallel to the axis of the shaft.

9. An abrasive wheel assembly for supporting and driving an abrasiveannulus by means of lateral flanges, said assembly comprising a drivingshaft provided on one side of the wheel with right-hand threads and onthe opposite side with left-hand threads, a pair of correspondinglythreaded driving flanges mounted on the threaded portions of the drivingshaft, an abrasive annulus supported in both radial and axial directionsby said driving flanges, and permanently elastic means for compensatingbetween the axial expansions of said shaft and abrasive annulus, saidmeans comprising a'pair of plates inserted between one side of. theabrasive annulus and its adjacent driving flange, the two plates beingprovided with interlocking lugs for the transmission of torque whilepermitting relative axial movement of the plates, and corrugated springsradially disposed between the plates to resist axial pressure exerted bythe flanges on the sides of the abrasive wheel.

10. An abrasive wheel assembly comprising an contacts, and acompensating annular member interposed between at least one of saidflanges and the abrasive annulus to compensate for differences betweenthe axial expansions of said shaft and abrasive annulus respectively,said compensating annular, member having a high eoefiicient of thermalexpansion relative to that of the abrasive annulus and an axialdimension determined from its coemcient of expansion and those of thedriving shaft and abrasive annulus to substantially compensate fortemperature changes of the order of, one hundred degrees centigrade,said compensating annular member being composed of one or more of thegroup of materials including synthetic resins and sulphur -inixtures. A

11. Anabrasive wheel assembly comprising an abrasive annulus, right andleft hand threaded driving flanges mounted t o/turn on a.correspondingly threaded driving shaft and to transmit power to theabrasive annulus with the aid of axial pressure, and a compensatingannular member disposed between at least one of said flanges and theabrasive annulus and having an axial length and a coeiflcient ofexpansion of such magnitudes as to substantially compensate fordiflerences of expansion between said driv- 'ing shaft and said abrasiveannulus, said compensating annular member being composed mainly ofsulphur.

12. An abrasive wheel assembly comprising an abrasive annulus, right andleft-hand threaded driving flanges mounted to turn on a correspondinglythreaded driving shaft for transmitting power to the abrasive annuluswith the aid of axial pressure, and a compensating annular memberdisposed between at least one of said flanges and the abrasive annulusand having an axial length and coefficient of expansion of suchmagnitudes as to substantially compensate for differences of expansionbetween said driving shaft and said abrasive annulus, said compensatingmainly of a synthetic resin which has been hardened in 'situ.

ALBERT L. BALL.

RAYMOND C. BENNER.

annular member being composed

